Vaccination offers protection against future exposure to pathogens because it triggers clonal expansion of lymphocytes
Importance of alive and dead vaccines
Infectious agents (viruses or bacteria) whose virulence has been reduced by a series of treatments are used in live attenuated vaccines.
Following vaccination or spontaneous infection, the pathogen causes lymphocyte proliferation that recognizes its antigens and forms a long-lasting immunological "memory."
Hence, the correct answer is option B
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